System and method for inline tiering of write data

ABSTRACT

A method, computer program product, and computer system for receiving, by a computing device, new data to write to a leaf. At least two timestamps of the leaf may be examined. It may be determined whether a time interval between the at least two timestamps of the leaf is greater than an age threshold. The new data may be written to a first tier storage device when the time interval between the at least two timestamps of the leaf is less than the age threshold; The new data may be written to a second tier storage device when the time interval between the at least two timestamps of the leaf is greater than the age threshold.

BACKGROUND

In some log-structured storage systems, all writes (ingest) into thesystem are generally bound to new log-locations rather than over-writingthe data's existing location. If the storage system contains drives ofdifferent performance and endurance (e.g., writes-per-day)characteristics and thereby creating tiers of different types, then adecision needs to be made about which tier into which to log-write thedata.

Generally, existing strategies assume that all new data being writteninto the system is “hot” data and is thus written to the tier with thehighest performance and endurance characteristics. Subsequently, in thebackground, e.g., as part of garbage-collection or otherwise, the datais cleaned/moved into the same tier (in-tier) if the data is still hotor cleaned/moved into a lower tier (down-tier) if the data is not hotanymore.

BRIEF SUMMARY OF DISCLOSURE

In one example implementation, a method, performed by one or morecomputing devices, may include but is not limited to receiving, by acomputing device, new data to write to a leaf. At least two timestampsof the leaf may be examined. It may be determined whether a timeinterval between the at least two timestamps of the leaf is greater thanan age threshold. The new data may be written to a first tier storagedevice when the time interval between the at least two timestamps of theleaf is less than the age threshold; The new data may be written to asecond tier storage device when the time interval between the at leasttwo timestamps of the leaf is greater than the age threshold.

One or more of the following example features may be included. The atleast two timestamps may include three timestamps. The new data may bewritten to the second tier storage device when the time interval betweena first and a second timestamp of the at least two timestamps of theleaf and a second time interval between the second timestamp and a thirdtimestamp of the at least two timestamps of the leaf are greater thanthe age threshold. The age threshold may be based upon, at least inpart, a current garbage collection queue. The age threshold may beadjusted based upon, at least in part, the current garbage collectionqueue. The age threshold may be adjusted down when fewer physical largeblocks (PLBs) are identified with the age threshold as a candidate forgarbage collection than are capable of being added to the currentgarbage collection queue. The age threshold may be adjusted up when morePLBs are identified with the age threshold as the candidate for garbagecollection than are capable of being added to the current garbagecollection queue.

In another example implementation, a computing system may include one ormore processors and one or more memories configured to performoperations that may include but are not limited to receiving new data towrite to a leaf. At least two timestamps of the leaf may be examined. Itmay be determined whether a time interval between the at least twotimestamps of the leaf is greater than an age threshold. The new datamay be written to a first tier storage device when the time intervalbetween the at least two timestamps of the leaf is less than the agethreshold; The new data may be written to a second tier storage devicewhen the time interval between the at least two timestamps of the leafis greater than the age threshold.

One or more of the following example features may be included. The atleast two timestamps may include three timestamps. The new data may bewritten to the second tier storage device when the time interval betweena first and a second timestamp of the at least two timestamps of theleaf and a second time interval between the second timestamp and a thirdtimestamp of the at least two timestamps of the leaf are greater thanthe age threshold. The age threshold may be based upon, at least inpart, a current garbage collection queue. The age threshold may beadjusted based upon, at least in part, the current garbage collectionqueue. The age threshold may be adjusted down when fewer physical largeblocks (PLBs) are identified with the age threshold as a candidate forgarbage collection than are capable of being added to the currentgarbage collection queue. The age threshold may be adjusted up when morePLBs are identified with the age threshold as the candidate for garbagecollection than are capable of being added to the current garbagecollection queue.

In another example implementation, a computer program product may resideon a computer readable storage medium having a plurality of instructionsstored thereon which, when executed across one or more processors, maycause at least a portion of the one or more processors to performoperations that may include but are not limited to receiving new data towrite to a leaf. At least two timestamps of the leaf may be examined. Itmay be determined whether a time interval between the at least twotimestamps of the leaf is greater than an age threshold. The new datamay be written to a first tier storage device when the time intervalbetween the at least two timestamps of the leaf is less than the agethreshold; The new data may be written to a second tier storage devicewhen the time interval between the at least two timestamps of the leafis greater than the age threshold.

One or more of the following example features may be included. The atleast two timestamps may include three timestamps. The new data may bewritten to the second tier storage device when the time interval betweena first and a second timestamp of the at least two timestamps of theleaf and a second time interval between the second timestamp and a thirdtimestamp of the at least two timestamps of the leaf are greater thanthe age threshold. The age threshold may be based upon, at least inpart, a current garbage collection queue. The age threshold may beadjusted based upon, at least in part, the current garbage collectionqueue. The age threshold may be adjusted down when fewer physical largeblocks (PLBs) are identified with the age threshold as a candidate forgarbage collection than are capable of being added to the currentgarbage collection queue. The age threshold may be adjusted up when morePLBs are identified with the age threshold as the candidate for garbagecollection than are capable of being added to the current garbagecollection queue.

The details of one or more example implementations are set forth in theaccompanying drawings and the description below. Other possible examplefeatures and/or possible example advantages will become apparent fromthe description, the drawings, and the claims. Some implementations maynot have those possible example features and/or possible exampleadvantages, and such possible example features and/or possible exampleadvantages may not necessarily be required of some implementations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example diagrammatic view of a tiering process coupled toan example distributed computing network according to one or moreexample implementations of the disclosure;

FIG. 2 is an example diagrammatic view of a storage system of FIG. 1according to one or more example implementations of the disclosure;

FIG. 3 is an example diagrammatic view of a storage target of FIG. 1according to one or more example implementations of the disclosure;

FIG. 4 is an example flowchart of a tiering process according to one ormore example implementations of the disclosure; and

FIG. 5 is an example diagrammatic view of a log structured storagesystem according to one or more example implementations of thedisclosure.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

System Overview:

In some implementations, the present disclosure may be embodied as amethod, system, or computer program product. Accordingly, in someimplementations, the present disclosure may take the form of an entirelyhardware implementation, an entirely software implementation (includingfirmware, resident software, micro-code, etc.) or an implementationcombining software and hardware aspects that may all generally bereferred to herein as a “circuit,” “module” or “system.” Furthermore, insome implementations, the present disclosure may take the form of acomputer program product on a computer-usable storage medium havingcomputer-usable program code embodied in the medium.

In some implementations, any suitable computer usable or computerreadable medium (or media) may be utilized. The computer readable mediummay be a computer readable signal medium or a computer readable storagemedium. The computer-usable, or computer-readable, storage medium(including a storage device associated with a computing device or clientelectronic device) may be, for example, but is not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, device, or any suitable combination ofthe foregoing. More specific examples (a non-exhaustive list) of thecomputer-readable medium may include the following: an electricalconnection having one or more wires, a portable computer diskette, ahard disk, a random access memory (RAM), a read-only memory (ROM), anerasable programmable read-only memory (EPROM or Flash memory), anoptical fiber, a portable compact disc read-only memory (CD-ROM), anoptical storage device, a digital versatile disk (DVD), a static randomaccess memory (SRAM), a memory stick, a floppy disk, a mechanicallyencoded device such as punch-cards or raised structures in a groovehaving instructions recorded thereon, a media such as those supportingthe internet or an intranet, or a magnetic storage device. Note that thecomputer-usable or computer-readable medium could even be a suitablemedium upon which the program is stored, scanned, compiled, interpreted,or otherwise processed in a suitable manner, if necessary, and thenstored in a computer memory. In the context of the present disclosure, acomputer-usable or computer-readable, storage medium may be any tangiblemedium that can contain or store a program for use by or in connectionwith the instruction execution system, apparatus, or device.

In some implementations, a computer readable signal medium may include apropagated data signal with computer readable program code embodiedtherein, for example, in baseband or as part of a carrier wave. In someimplementations, such a propagated signal may take any of a variety offorms, including, but not limited to, electro-magnetic, optical, or anysuitable combination thereof. In some implementations, the computerreadable program code may be transmitted using any appropriate medium,including but not limited to the internet, wireline, optical fibercable, RF, etc. In some implementations, a computer readable signalmedium may be any computer readable medium that is not a computerreadable storage medium and that can communicate, propagate, ortransport a program for use by or in connection with an instructionexecution system, apparatus, or device.

In some implementations, computer program code for carrying outoperations of the present disclosure may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Java®, Smalltalk, C++ or the like.Java® and all Java-based trademarks and logos are trademarks orregistered trademarks of Oracle and/or its affiliates. However, thecomputer program code for carrying out operations of the presentdisclosure may also be written in conventional procedural programminglanguages, such as the “C” programming language, PASCAL, or similarprogramming languages, as well as in scripting languages such asJavascript, PERL, or Python. The program code may execute entirely onthe user's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough a local area network (LAN) or a wide area network (WAN), or theconnection may be made to an external computer (for example, through theinternet using an Internet Service Provider). In some implementations,electronic circuitry including, for example, programmable logiccircuitry, field-programmable gate arrays (FPGAs) or other hardwareaccelerators, micro-controller units (MCUs), or programmable logicarrays (PLAs) may execute the computer readable programinstructions/code by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present disclosure.

In some implementations, the flowchart and block diagrams in the figuresillustrate the architecture, functionality, and operation of possibleimplementations of apparatus (systems), methods and computer programproducts according to various implementations of the present disclosure.Each block in the flowchart and/or block diagrams, and combinations ofblocks in the flowchart and/or block diagrams, may represent a module,segment, or portion of code, which comprises one or more executablecomputer program instructions for implementing the specified logicalfunction(s)/act(s). These computer program instructions may be providedto a processor of a general purpose computer, special purpose computer,or other programmable data processing apparatus to produce a machine,such that the computer program instructions, which may execute via theprocessor of the computer or other programmable data processingapparatus, create the ability to implement one or more of thefunctions/acts specified in the flowchart and/or block diagram block orblocks or combinations thereof. It should be noted that, in someimplementations, the functions noted in the block(s) may occur out ofthe order noted in the figures (or combined or omitted). For example,two blocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved.

In some implementations, these computer program instructions may also bestored in a computer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including instruction meanswhich implement the function/act specified in the flowchart and/or blockdiagram block or blocks or combinations thereof.

In some implementations, the computer program instructions may also beloaded onto a computer or other programmable data processing apparatusto cause a series of operational steps to be performed (not necessarilyin a particular order) on the computer or other programmable apparatusto produce a computer implemented process such that the instructionswhich execute on the computer or other programmable apparatus providesteps for implementing the functions/acts (not necessarily in aparticular order) specified in the flowchart and/or block diagram blockor blocks or combinations thereof.

Referring now to the example implementation of FIG. 1, there is showntiering process 10 that may reside on and may be executed by a computer(e.g., computer 12), which may be connected to a network (e.g., network14) (e.g., the internet or a local area network). Examples of computer12 (and/or one or more of the client electronic devices noted below) mayinclude, but are not limited to, a storage system (e.g., a NetworkAttached Storage (NAS) system, a Storage Area Network (SAN)), a personalcomputer(s), a laptop computer(s), mobile computing device(s), a servercomputer, a series of server computers, a mainframe computer(s), or acomputing cloud(s). As is known in the art, a SAN may include one ormore of the client electronic devices, including a RAID device and a NASsystem. In some implementations, each of the aforementioned may begenerally described as a computing device. In certain implementations, acomputing device may be a physical or virtual device. In manyimplementations, a computing device may be any device capable ofperforming operations, such as a dedicated processor, a portion of aprocessor, a virtual processor, a portion of a virtual processor,portion of a virtual device, or a virtual device. In someimplementations, a processor may be a physical processor or a virtualprocessor. In some implementations, a virtual processor may correspondto one or more parts of one or more physical processors. In someimplementations, the instructions/logic may be distributed and executedacross one or more processors, virtual or physical, to execute theinstructions/logic. Computer 12 may execute an operating system, forexample, but not limited to, Microsoft® Windows® Mac® OS X®; Red Hat®Linux®, Windows® Mobile, Chrome OS, Blackberry OS, Fire OS, or a customoperating system. (Microsoft and Windows are registered trademarks ofMicrosoft Corporation in the United States, other countries or both; Macand OS X are registered trademarks of Apple Inc. in the United States,other countries or both; Red Hat is a registered trademark of Red HatCorporation in the United States, other countries or both; and Linux isa registered trademark of Linus Torvalds in the United States, othercountries or both).

In some implementations, as will be discussed below in greater detail, atiering process, such as tiering process 10 of FIG. 1, may receive, by acomputing device, new data to write to a leaf. At least two timestampsof the leaf may be examined. It may be determined whether a timeinterval between the at least two timestamps of the leaf is greater thanan age threshold. The new data may be written to a first tier storagedevice when the time interval between the at least two timestamps of theleaf is less than the age threshold; The new data may be written to asecond tier storage device when the time interval between the at leasttwo timestamps of the leaf is greater than the age threshold.

In some implementations, the instruction sets and subroutines of tieringprocess 10, which may be stored on storage device, such as storagedevice 16, coupled to computer 12, may be executed by one or moreprocessors and one or more memory architectures included within computer12. In some implementations, storage device 16 may include but is notlimited to: a hard disk drive; all forms of flash memory storagedevices; a tape drive; an optical drive; a RAID array (or other array);a random access memory (RAM); a read-only memory (ROM); or combinationthereof. In some implementations, storage device 16 may be organized asan extent, an extent pool, a RAID extent (e.g., an example 4D+1P R5,where the RAID extent may include, e.g., five storage device extentsthat may be allocated from, e.g., five different storage devices), amapped RAID (e.g., a collection of RAID extents), or combinationthereof.

In some implementations, network 14 may be connected to one or moresecondary networks (e.g., network 18), examples of which may include butare not limited to: a local area network; a wide area network or othertelecommunications network facility; or an intranet, for example. Thephrase “telecommunications network facility,” as used herein, may referto a facility configured to transmit, and/or receive transmissionsto/from one or more mobile client electronic devices (e.g., cellphones,etc.) as well as many others.

In some implementations, computer 12 may include a data store, such as adatabase (e.g., relational database, object-oriented database,triplestore database, etc.) and may be located within any suitablememory location, such as storage device 16 coupled to computer 12. Insome implementations, data, metadata, information, etc. describedthroughout the present disclosure may be stored in the data store. Insome implementations, computer 12 may utilize any known databasemanagement system such as, but not limited to, DB2, in order to providemulti-user access to one or more databases, such as the above notedrelational database. In some implementations, the data store may also bea custom database, such as, for example, a flat file database or an XMLdatabase. In some implementations, any other form(s) of a data storagestructure and/or organization may also be used. In some implementations,tiering process 10 may be a component of the data store, a standaloneapplication that interfaces with the above noted data store and/or anapplet/application that is accessed via client applications 22, 24, 26,28. In some implementations, the above noted data store may be, in wholeor in part, distributed in a cloud computing topology. In this way,computer 12 and storage device 16 may refer to multiple devices, whichmay also be distributed throughout the network.

In some implementations, computer 12 may execute a storage managementapplication (e.g., storage management application 21), examples of whichmay include, but are not limited to, e.g., a storage system application,a cloud computing application, a data synchronization application, adata migration application, a garbage collection application, or otherapplication that allows for the implementation and/or management of datain a clustered (or non-clustered) environment (or the like). In someimplementations, tiering process 10 and/or storage managementapplication 21 may be accessed via one or more of client applications22, 24, 26, 28. In some implementations, tiering process 10 may be astandalone application, or may be an applet/application/script/extensionthat may interact with and/or be executed within storage managementapplication 21, a component of storage management application 21, and/orone or more of client applications 22, 24, 26, 28. In someimplementations, storage management application 21 may be a standaloneapplication, or may be an applet/application/script/extension that mayinteract with and/or be executed within tiering process 10, a componentof tiering process 10, and/or one or more of client applications 22, 24,26, 28. In some implementations, one or more of client applications 22,24, 26, 28 may be a standalone application, or may be anapplet/application/script/extension that may interact with and/or beexecuted within and/or be a component of tiering process 10 and/orstorage management application 21. Examples of client applications 22,24, 26, 28 may include, but are not limited to, e.g., a storage systemapplication, a cloud computing application, a data synchronizationapplication, a data migration application, a garbage collectionapplication, or other application that allows for the implementationand/or management of data in a clustered (or non-clustered) environment(or the like), a standard and/or mobile web browser, an emailapplication (e.g., an email client application), a textual and/or agraphical user interface, a customized web browser, a plugin, anApplication Programming Interface (API), or a custom application. Theinstruction sets and subroutines of client applications 22, 24, 26, 28,which may be stored on storage devices 30, 32, 34, 36, coupled to clientelectronic devices 38, 40, 42, 44, may be executed by one or moreprocessors and one or more memory architectures incorporated into clientelectronic devices 38, 40, 42, 44.

In some implementations, one or more of storage devices 30, 32, 34, 36,may include but are not limited to: hard disk drives; flash drives, tapedrives; optical drives; RAID arrays; random access memories (RAM); andread-only memories (ROM). Examples of client electronic devices 38, 40,42, 44 (and/or computer 12) may include, but are not limited to, apersonal computer (e.g., client electronic device 38), a laptop computer(e.g., client electronic device 40), a smart/data-enabled, cellularphone (e.g., client electronic device 42), a notebook computer (e.g.,client electronic device 44), a tablet, a server, a television, a smarttelevision, a smart speaker, an Internet of Things (IoT) device, a media(e.g., video, photo, etc.) capturing device, and a dedicated networkdevice. Client electronic devices 38, 40, 42, 44 may each execute anoperating system, examples of which may include but are not limited to,Android™, Apple® iOS®, Mac® OS X®; Red Hat® Linux®, Windows® Mobile,Chrome OS, Blackberry OS, Fire OS, or a custom operating system.

In some implementations, one or more of client applications 22, 24, 26,28 may be configured to effectuate some or all of the functionality oftiering process 10 (and vice versa). Accordingly, in someimplementations, tiering process 10 may be a purely server-sideapplication, a purely client-side application, or a hybridserver-side/client-side application that is cooperatively executed byone or more of client applications 22, 24, 26, 28 and/or tiering process10.

In some implementations, one or more of client applications 22, 24, 26,28 may be configured to effectuate some or all of the functionality ofstorage management application 21 (and vice versa). Accordingly, in someimplementations, storage management application 21 may be a purelyserver-side application, a purely client-side application, or a hybridserver-side/client-side application that is cooperatively executed byone or more of client applications 22, 24, 26, 28 and/or storagemanagement application 21. As one or more of client applications 22, 24,26, 28, tiering process 10, and storage management application 21, takensingly or in any combination, may effectuate some or all of the samefunctionality, any description of effectuating such functionality viaone or more of client applications 22, 24, 26, 28, tiering process 10,storage management application 21, or combination thereof, and anydescribed interaction(s) between one or more of client applications 22,24, 26, 28, tiering process 10, storage management application 21, orcombination thereof to effectuate such functionality, should be taken asan example only and not to limit the scope of the disclosure.

In some implementations, one or more of users 46, 48, 50, 52 may accesscomputer 12 and tiering process 10 (e.g., using one or more of clientelectronic devices 38, 40, 42, 44) directly through network 14 orthrough secondary network 18. Further, computer 12 may be connected tonetwork 14 through secondary network 18, as illustrated with phantomlink line 54. Tiering process 10 may include one or more userinterfaces, such as browsers and textual or graphical user interfaces,through which users 46, 48, 50, 52 may access tiering process 10.

In some implementations, the various client electronic devices may bedirectly or indirectly coupled to network 14 (or network 18). Forexample, client electronic device 38 is shown directly coupled tonetwork 14 via a hardwired network connection. Further, clientelectronic device 44 is shown directly coupled to network 18 via ahardwired network connection. Client electronic device 40 is shownwirelessly coupled to network 14 via wireless communication channel 56established between client electronic device 40 and wireless accesspoint (i.e., WAP) 58, which is shown directly coupled to network 14. WAP58 may be, for example, an IEEE 802.11a, 802.11b, 802.11g, 802.11n,802.11ac, Wi-Fi®, RFID, and/or Bluetooth™ (including Bluetooth™ LowEnergy) device that is capable of establishing wireless communicationchannel 56 between client electronic device 40 and WAP 58. Clientelectronic device 42 is shown wirelessly coupled to network 14 viawireless communication channel 60 established between client electronicdevice 42 and cellular network/bridge 62, which is shown by exampledirectly coupled to network 14.

In some implementations, some or all of the IEEE 802.11x specificationsmay use Ethernet protocol and carrier sense multiple access withcollision avoidance (i.e., CSMA/CA) for path sharing. The various802.11x specifications may use phase-shift keying (i.e., PSK) modulationor complementary code keying (i.e., CCK) modulation, for example.Bluetooth™ (including Bluetooth™ Low Energy) is a telecommunicationsindustry specification that allows, e.g., mobile phones, computers,smart phones, and other electronic devices to be interconnected using ashort-range wireless connection. Other forms of interconnection (e.g.,Near Field Communication (NFC)) may also be used.

In some implementations, various I/O requests (e.g., I/O request 15) maybe sent from, e.g., client applications 22, 24, 26, 28 to, e.g.,computer 12. Examples of I/O request 15 may include but are not limitedto, data write requests (e.g., a request that content be written tocomputer 12) and data read requests (e.g., a request that content beread from computer 12).

Data Storage System:

Referring also to the example implementation of FIGS. 2-3 (e.g., wherecomputer 12 may be configured as a data storage system), computer 12 mayinclude storage processor 100 and a plurality of storage targets (e.g.,storage targets 102, 104, 106, 108, 110). In some implementations,storage targets 102, 104, 106, 108, 110 may include any of theabove-noted storage devices. In some implementations, storage targets102, 104, 106, 108, 110 may be configured to provide various levels ofperformance and/or high availability. For example, storage targets 102,104, 106, 108, 110 may be configured to form a non-fully-duplicativefault-tolerant data storage system (such as a non-fully-duplicative RAIDdata storage system), examples of which may include but are not limitedto: RAID 3 arrays, RAID 4 arrays, RAID 5 arrays, and/or RAID 6 arrays.It will be appreciated that various other types of RAID arrays may beused without departing from the scope of the present disclosure.

While in this particular example, computer 12 is shown to include fivestorage targets (e.g., storage targets 102, 104, 106, 108, 110), this isfor example purposes only and is not intended limit the presentdisclosure. For instance, the actual number of storage targets may beincreased or decreased depending upon, e.g., the level ofredundancy/performance/capacity required.

Further, the storage targets (e.g., storage targets 102, 104, 106, 108,110) included with computer 12 may be configured to form a plurality ofdiscrete storage arrays. For instance, and assuming for example purposesonly that computer 12 includes, e.g., ten discrete storage targets, afirst five targets (of the ten storage targets) may be configured toform a first RAID array and a second five targets (of the ten storagetargets) may be configured to form a second RAID array.

In some implementations, one or more of storage targets 102, 104, 106,108, 110 may be configured to store coded data (e.g., via storagemanagement process 21), wherein such coded data may allow for theregeneration of data lost/corrupted on one or more of storage targets102, 104, 106, 108, 110. Examples of such coded data may include but isnot limited to parity data and Reed-Solomon data. Such coded data may bedistributed across all of storage targets 102, 104, 106, 108, 110 or maybe stored within a specific storage target.

Examples of storage targets 102, 104, 106, 108, 110 may include one ormore data arrays, wherein a combination of storage targets 102, 104,106, 108, 110 (and any processing/control systems associated withstorage management application 21) may form data array 112.

The manner in which computer 12 is implemented may vary depending upone.g., the level of redundancy/performance/capacity required. Forexample, computer 12 may be configured as a SAN (i.e., a Storage AreaNetwork), in which storage processor 100 may be, e.g., a dedicatedcomputing system and each of storage targets 102, 104, 106, 108, 110 maybe a RAID device. An example of storage processor 100 may include but isnot limited to a VPLEX™ system offered by Dell EMC™ of Hopkinton, Mass.

In the example where computer 12 is configured as a SAN, the variouscomponents of computer 12 (e.g., storage processor 100, and storagetargets 102, 104, 106, 108, 110) may be coupled using networkinfrastructure 114, examples of which may include but are not limited toan Ethernet (e.g., Layer 2 or Layer 3) network, a fiber channel network,an InfiniBand network, or any other circuit switched/packet switchednetwork.

As discussed above, various I/O requests (e.g., I/O request 15) may begenerated. For example, these I/O requests may be sent from, e.g.,client applications 22, 24, 26, 28 to, e.g., computer 12.Additionally/alternatively (e.g., when storage processor 100 isconfigured as an application server or otherwise), these I/O requestsmay be internally generated within storage processor 100 (e.g., viastorage management process 21). Examples of I/O request 15 may includebut are not limited to data write request 116 (e.g., a request thatcontent 118 be written to computer 12) and data read request 120 (e.g.,a request that content 118 be read from computer 12).

In some implementations, during operation of storage processor 100,content 118 to be written to computer 12 may be received and/orprocessed by storage processor 100 (e.g., via storage management process21). Additionally/alternatively (e.g., when storage processor 100 isconfigured as an application server or otherwise), content 118 to bewritten to computer 12 may be internally generated by storage processor100 (e.g., via storage management process 21).

As discussed above, the instruction sets and subroutines of storagemanagement application 21, which may be stored on storage device 16included within computer 12, may be executed by one or more processorsand one or more memory architectures included with computer 12.Accordingly, in addition to being executed on storage processor 100,some or all of the instruction sets and subroutines of storagemanagement application 21 (and/or tiering process 10) may be executed byone or more processors and one or more memory architectures includedwith data array 112.

In some implementations, storage processor 100 may include front endcache memory system 122. Examples of front end cache memory system 122may include but are not limited to a volatile, solid-state, cache memorysystem (e.g., a dynamic RAM cache memory system), a non-volatile,solid-state, cache memory system (e.g., a flash-based, cache memorysystem), and/or any of the above-noted storage devices.

In some implementations, storage processor 100 may initially storecontent 118 within front end cache memory system 122. Depending upon themanner in which front end cache memory system 122 is configured, storageprocessor 100 (e.g., via storage management process 21) may immediatelywrite content 118 to data array 112 (e.g., if front end cache memorysystem 122 is configured as a write-through cache) or may subsequentlywrite content 118 to data array 112 (e.g., if front end cache memorysystem 122 is configured as a write-back cache).

In some implementations, one or more of storage targets 102, 104, 106,108, 110 may include a backend cache memory system. Examples of thebackend cache memory system may include but are not limited to avolatile, solid-state, cache memory system (e.g., a dynamic RAM cachememory system), a non-volatile, solid-state, cache memory system (e.g.,a flash-based, cache memory system), and/or any of the above-notedstorage devices.

Storage Targets:

As discussed above, one or more of storage targets 102, 104, 106, 108,110 may be a RAID device. For instance, and referring also to FIG. 3,there is shown example target 150, wherein target 150 may be one exampleimplementation of a RAID implementation of, e.g., storage target 102,storage target 104, storage target 106, storage target 108, and/orstorage target 110. An example of target 150 may include but is notlimited to a VNX™ system offered by Dell EMC™ of Hopkinton, Mass.Examples of storage devices 154, 156, 158, 160, 162 may include one ormore electro-mechanical hard disk drives, one or more solid-state/flashdevices, and/or any of the above-noted storage devices. It will beappreciated that while the term “disk” or “drive” may be usedthroughout, these may refer to and be used interchangeably with anytypes of appropriate storage devices as the context and functionality ofthe storage device permits.

In some implementations, target 150 may include storage processor 152and a plurality of storage devices (e.g., storage devices 154, 156, 158,160, 162). Storage devices 154, 156, 158, 160, 162 may be configured toprovide various levels of performance and/or high availability (e.g.,via storage management process 21). For example, one or more of storagedevices 154, 156, 158, 160, 162 (or any of the above-noted storagedevices) may be configured as a RAID 0 array, in which data is stripedacross storage devices. By striping data across a plurality of storagedevices, improved performance may be realized. However, RAID 0 arraysmay not provide a level of high availability. Accordingly, one or moreof storage devices 154, 156, 158, 160, 162 (or any of the above-notedstorage devices) may be configured as a RAID 1 array, in which data ismirrored between storage devices. By mirroring data between storagedevices, a level of high availability may be achieved as multiple copiesof the data may be stored within storage devices 154, 156, 158, 160,162.

While storage devices 154, 156, 158, 160, 162 are discussed above asbeing configured in a RAID 0 or RAID 1 array, this is for examplepurposes only and not intended to limit the present disclosure, as otherconfigurations are possible. For example, storage devices 154, 156, 158,160, 162 may be configured as a RAID 3, RAID 4, RAID 5 or RAID 6 array.

While in this particular example, target 150 is shown to include fivestorage devices (e.g., storage devices 154, 156, 158, 160, 162), this isfor example purposes only and not intended to limit the presentdisclosure. For instance, the actual number of storage devices may beincreased or decreased depending upon, e.g., the level ofredundancy/performance/capacity required.

In some implementations, one or more of storage devices 154, 156, 158,160, 162 may be configured to store (e.g., via storage managementprocess 21) coded data, wherein such coded data may allow for theregeneration of data lost/corrupted on one or more of storage devices154, 156, 158, 160, 162. Examples of such coded data may include but arenot limited to parity data and Reed-Solomon data. Such coded data may bedistributed across all of storage devices 154, 156, 158, 160, 162 or maybe stored within a specific storage device.

The manner in which target 150 is implemented may vary depending upone.g., the level of redundancy/performance/capacity required. Forexample, target 150 may be a RAID device in which storage processor 152is a RAID controller card and storage devices 154, 156, 158, 160, 162are individual “hot-swappable” hard disk drives. Another example oftarget 150 may be a RAID system, examples of which may include but arenot limited to an NAS (i.e., Network Attached Storage) device or a SAN(i.e., Storage Area Network).

In some implementations, storage target 150 may execute all or a portionof storage management application 21. The instruction sets andsubroutines of storage management application 21, which may be stored ona storage device (e.g., storage device 164) coupled to storage processor152, may be executed by one or more processors and one or more memoryarchitectures included with storage processor 152. Storage device 164may include but is not limited to any of the above-noted storagedevices.

As discussed above, computer 12 may be configured as a SAN, whereinstorage processor 100 may be a dedicated computing system and each ofstorage targets 102, 104, 106, 108, 110 may be a RAID device.Accordingly, when storage processor 100 processes data requests 116,120, storage processor 100 (e.g., via storage management process 21) mayprovide the appropriate requests/content (e.g., write request 166,content 168 and read request 170) to, e.g., storage target 150 (which isrepresentative of storage targets 102, 104, 106, 108 and/or 110).

In some implementations, during operation of storage processor 152,content 168 to be written to target 150 may be processed by storageprocessor 152 (e.g., via storage management process 21). Storageprocessor 152 may include cache memory system 172. Examples of cachememory system 172 may include but are not limited to a volatile,solid-state, cache memory system (e.g., a dynamic RAM cache memorysystem) and/or a non-volatile, solid-state, cache memory system (e.g., aflash-based, cache memory system). During operation of storage processor152, content 168 to be written to target 150 may be received by storageprocessor 152 (e.g., via storage management process 21) and initiallystored (e.g., via storage management process 21) within front end cachememory system 172.

In some log-structured storage systems, all writes (ingest) into thesystem are generally bound to new log-locations rather than over-writingthe data's existing location. If the storage system contains drives ofdifferent performance and endurance (e.g., writes-per-day)characteristics and thereby creating tiers of different types, then adecision needs to be made about which tier into which to log-write thedata.

Generally, existing strategies assume that all new data being writteninto the system is “hot” data and is thus written to the tier with thehighest performance and endurance characteristics. Subsequently, in thebackground, e.g., as part of garbage-collection or otherwise, the datais cleaned/moved into the same tier (in-tier) if the data is still hotor cleaned/moved into a lower tier (down-tier) if the data is not hotanymore.

This approach suffers if the new data coming into the system is alreadycold to begin with. In this case, writing the data to the highest tierand then as part of garbage-collection (or otherwise), down-tiering itto lower tiers until the data reaches its final location in the lowesttier would be wasteful. For instance, it takes away the performance ofthe higher tiers, which may be used for hot data, and may also causewrite-amplification.

Accordingly, as will be discussed below, rather than assuming that allnew data being written into the system is hot data and thus written tothe tier with the highest performance and endurance characteristics, thepresent disclosure may track and predict the temperature of inline writedata (ingest), so that the new data being written into the system mayfirst be written to the tier whose performance/endurance characteristicsmatch with the temperature of the data.

The Tiering Process:

As discussed above and referring also at least to the exampleimplementations of FIGS. 4-5, tiering process 10 may receive 400, by acomputing device, new data to write to a leaf. Tiering process 10 mayexamine 402 at least two timestamps of the leaf. Tiering process 10 maydetermine 404 whether a time interval between the at least twotimestamps of the leaf is greater than an age threshold. Tiering process10 may write 406 the new data to a first tier storage device when thetime interval between the at least two timestamps of the leaf is lessthan the age threshold. Tiering process 10 may write 408 the new data toa second tier storage device when the time interval between the at leasttwo timestamps of the leaf is greater than the age threshold.

In some implementations, tiering process 10 may receive 400, by acomputing device, new data to write to a leaf. For instance, andreferring at least to the example FIG. 5, an example logicaldiagrammatic view of a log structured storage system is shown. In astorage system, to support features such as thin-provisioning, snapshotsand deduplication, logical address space out of which volumes arecreated may be mapped to log-structured address space using a tree likedata-structure. For example, n-way (e.g., where n=512) tree with a depthof 3 (Top-node, Mid-node, Leaf-node) may describe 2 MB of log-space at4k block size. The 3-level indirection scheme to access user data may beas follows:

Leaf: Logical Block Address (LBA) representation layer, generallyorganized as a tree. Each leaf entry generally corresponds to a specificLBA range.

Virtual Large Block (VLB): Isolates LBA layer from physical storage.Encapsulates physical location of the user data and allows datarelocation without necessity to update Leafs.

Physical Large Block (PLB): In log structured systems, the data isstored in contiguous chunks of data, called PLB (e.g., 2 MB chunks). Theactual user data pages reside inside, and they may be referenced by oneor more VLBs.

As such, the structure may be generally described as: Leaf (LBArepresentation)→Virtual Block (VLB)→Physical Block (PLB).

For example, after a write operation: Leaf, corresponding to LBA willpoint to VLB that contains references to PLBs where the user data isstored. As such, in the example, tiering process 10 may receive 400 newdata to write to a leaf (e.g., leaf 502).

In some implementations, tiering process 10 may examine 402 at least twotimestamps of the leaf. For example, the “temperature” (i.e., how oftendata is accessed) of the logical address space may be tracked by puttinga set of time-stamps in each of the leaf nodes (e.g., leaf 502)describing that logical address space. For example, data frequentlywritten to a leaf (e.g., a PLB pointed to by the leaf and VLB) would beconsidered “hot” and thus would be stored in a higher tiered storagedevice (e.g., a storage device with higher performance), whereas datainfrequently written to a leaf would be considered “cold” and thus wouldbe stored in a lower tiered storage device (e.g., a storage device withlower performance). Granularity of the logical address space (e.g.,LUN/volume) on which temperature is tracked may be based on a number oftimestamp stored in the individual leaf node. For example, thegranularity may be 2 MB with one set of timestamps in the leaf or 1 MBwith two sets of timestamps in the leaf (e.g., Top maps 512 GB; Mid maps1 GB, Leaf maps 2 MB). In the example, tiering process 10 may examine402 at least some of the timestamps of the leaf to determine thetemperature of the incoming write data associated with being written tothe leaf (e.g., the PLB of leaf 502). For instance, tiering process 10may scan two timestamps (e.g., in the PLB descriptors) to determine atime interval between those two timestamps. As will be discussed below,tiering process 10 may also examine three timestamps to determine a timeinterval between the first and second timestamp, and the time intervalbetween the second and third timestamp.

In some implementations, tiering process 10 may determine 404 whether atime interval between the at least two timestamps of the leaf is greaterthan an age threshold. For instance, using these timestamps, tieringprocess 10 may track the times of the latest writes into thelogical-address-space described by the leaf. These timestamps may thenhelp predict the hotness/coldness of the new write data into the leaf.To decide hotness/coldness, metrics of garbage collection functionalitymay be leveraged. In a log-structured system, garbage collection isgenerally required to clean up the holes generated in the log-space dueto overwrites. Garbage collection is typically most effective when thesegments it selects to clean are cold (e.g., data in those segments arenot taking any overwrites). To determine which segments are cold,garbage collection may place a timestamp of the latest overwrite in eachsegment, which it may then scan all the segments and pick the segmentswith oldest timestamps. This may be generally referred to asgarbage-collection age threshold for selecting segment to clean. Forexample, garbage-collection could be picking segments that are olderthan 30 days (based upon the oldest timestamps); that is, the lastoverwrite in the segment was at least 30 days back.

In some implementations, tiering process 10 may write 406 the new datato a first tier storage device when the time interval between the atleast two timestamps of the leaf is less than the age threshold, and maywrite 408 the new data to a second tier storage device when the timeinterval between the at least two timestamps of the leaf is greater thanthe age threshold. For example, based on the data structures describedand the functionality of garbage collection, inline tiering ofwrite-data may occur as follows: each set of examined timestamps in theleaf may be a set of three timestamps (or only two timestamps). Forinstance, if the time interval between the first and second timestamp isgreater than garbage collection age threshold, then the new data beingwritten to the leaf would be considered cold data (and thus written tothe lower tier). Conversely, if the time interval between the first andsecond timestamp is less than garbage collection age threshold, then thenew data being written to the leaf would be considered hot data (andthus written to the higher tier).

In some implementations, the new data may be written to the second tierstorage device when the time interval between a first and a secondtimestamp of the at least two timestamps of the leaf and a second timeinterval between the second timestamp and a third timestamp of the atleast two timestamps of the leaf are greater than the age threshold. Forinstance, to help ensure that the time interval of the timestamps wasnot an outlier situation (i.e., the data is frequently written to, butfor whatever reason the most recent two timestamps may not reflect thisif the most recent data was not written similarly as frequent), the timeinterval between second and third timestamp may also be examined. Inthis case, if the time interval between second and third timestamp isalso greater than garbage collection age threshold (like the first andsecond timestamp), then the new data being written to the leaf would beconsidered cold data (and thus written to the lower tier), whereas ifthe time interval between second and third timestamp is also less thangarbage collection age threshold (like the first and second timestamp),then the new data being written to the leaf would be considered hot data(and thus written to the higher tier). As such, the log tier selectedfor this new write data may be the same log tier that garbage collectionwould have normally selected to place the data it cleans from the coldsegments (segments that meet garbage collection age threshold), but maydo so inline (i.e., as the data is coming in rather than simply assumingthe data is hot and storing it in the higher tier, where it wouldsubsequently be placed into the appropriate tier based on temperatureduring garbage collection).

In some implementations, the age threshold may be based upon, at leastin part, a current garbage collection queue, and in someimplementations, tiering process 10 may adjust 410 the age thresholdbased upon, at least in part, the current garbage collection queue. Forinstance, the garbage collection queue may only be large enough to holda specific number of physical large blocks (PLBs) for garbagecollection. Thus, in the example, the age threshold may be adjustedbased upon the garbage collection queue to maximize efficiency.

For example, in some implementations, the age threshold may be adjusteddown when fewer physical large blocks (PLB s) are identified with theage threshold as a candidate for garbage collection than are capable ofbeing added to the current garbage collection queue. For instance,assume for example purposes only that the garbage collection queue canhold X PLBs. In the example, further assume that the age threshold is 30days, which results in identifying X-20 PLBs. Since 20 additional PLBscould potentially be added to the garbage collection queue, tieringprocess 10 may adjust the age threshold down (e.g., 25 days) to identifymore PLBs to be added to the garbage collection queue.

Similarly, the age threshold may be adjusted up when more PLBs areidentified with the age threshold as the candidate for garbagecollection than are capable of being added to the current garbagecollection queue. For instance, assume for example purposes only thatthe garbage collection queue can hold X PLBs. In the example, furtherassume that the age threshold is 25 days, which results in identifyingX+20 PLBs. Since there are 20 additional PLBs than are capable of beingadded to the garbage collection queue, tiering process 10 may adjust theage threshold up (e.g., 27 days) to identify less PLBs to be added tothe garbage collection queue. As such, the age threshold may bedynamically adjusted based upon the current garbage collection queue.

The terminology used herein is for the purpose of describing particularimplementations only and is not intended to be limiting of thedisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. As used herein, the language “at least one of A, B,and C” (and the like) should be interpreted as covering only A, only B,only C, or any combination of the three, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps (notnecessarily in a particular order), operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps (not necessarily in a particular order),operations, elements, components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents (e.g., ofall means or step plus function elements) that may be in the claimsbelow are intended to include any structure, material, or act forperforming the function in combination with other claimed elements asspecifically claimed. The description of the present disclosure has beenpresented for purposes of illustration and description, but is notintended to be exhaustive or limited to the disclosure in the formdisclosed. Many modifications, variations, substitutions, and anycombinations thereof will be apparent to those of ordinary skill in theart without departing from the scope and spirit of the disclosure. Theimplementation(s) were chosen and described in order to explain theprinciples of the disclosure and the practical application, and toenable others of ordinary skill in the art to understand the disclosurefor various implementation(s) with various modifications and/or anycombinations of implementation(s) as are suited to the particular usecontemplated.

Having thus described the disclosure of the present application indetail and by reference to implementation(s) thereof, it will beapparent that modifications, variations, and any combinations ofimplementation(s) (including any modifications, variations,substitutions, and combinations thereof) are possible without departingfrom the scope of the disclosure defined in the appended claims.

What is claimed is:
 1. A computer-implemented method comprising:receiving, by a computing device, new data to write to a leaf; examiningat least three timestamps of the leaf, wherein the at least threetimestamps are configured to track a temperature of a logical addressspace and include a latest write into the logical address space of theleaf; determining whether a time interval among the at least threetimestamps of the leaf is greater than an age threshold; writing the newdata to a first tier storage device when the time interval among the atleast three timestamps of the leaf is less than the age threshold; andwriting the new data to a second tier storage device when the timeinterval between a first and a second timestamp of the at least threetimestamps of the leaf and a second time interval between the secondtimestamp and a third timestamp of the at least three timestamps of theleaf are greater than the age threshold.
 2. The computer-implementedmethod of claim 1 wherein the age threshold is based upon, at least inpart, a current garbage collection queue.
 3. The computer-implementedmethod of claim 2 further comprising adjusting the age threshold basedupon, at least in part, the current garbage collection queue.
 4. Thecomputer-implemented method of claim 3 wherein the age threshold isadjusted down when fewer physical large blocks (PLBs) are identifiedwith the age threshold as a candidate for garbage collection than arecapable of being added to the current garbage collection queue.
 5. Thecomputer-implemented method of claim 4 wherein the age threshold isadjusted up when more PLBs are identified with the age threshold as thecandidate for garbage collection than are capable of being added to thecurrent garbage collection queue.
 6. A computer program product residingon a non-transitory computer readable storage medium having a pluralityof instructions stored thereon which, when executed across one or moreprocessors, causes at least a portion of the one or more processors toperform operations comprising: receiving new data to write to a leaf;examining at least three timestamps of the leaf, wherein the at leastthree timestamps are configured to track a temperature of a logicaladdress space and include a latest write into the logical address spaceof the leaf; determining whether a time interval among the at leastthree timestamps of the leaf is greater than an age threshold; writingthe new data to a first tier storage device when the time interval amongthe at least three timestamps of the leaf is less than the agethreshold; and writing the new data to a second tier storage device whenthe time interval between a first and a second timestamp of the at leastthree timestamps of the leaf and a second time interval between thesecond timestamp and a third timestamp of the at least three timestampsof the leaf are greater than the age threshold.
 7. The computer programproduct of claim 6 wherein the age threshold is based upon, at least inpart, a current garbage collection queue.
 8. The computer programproduct of claim 7 wherein the operations further comprise adjusting theage threshold based upon, at least in part, the current garbagecollection queue.
 9. The computer program product of claim 8 wherein theage threshold is adjusted down when fewer physical large blocks (PLBs)are identified with the age threshold as a candidate for garbagecollection than are capable of being added to the current garbagecollection queue.
 10. The computer program product of claim 9 whereinthe age threshold is adjusted up when more PLB s are identified with theage threshold as the candidate for garbage collection than are capableof being added to the current garbage collection queue.
 11. A computingsystem including one or more processors and one or more memoriesconfigured to perform operations comprising: receiving new data to writeto a leaf; examining at least three timestamps of the leaf, wherein theat least three timestamps are configured to track a temperature of alogical address space and include a latest write into the logicaladdress space of the leaf; determining whether a time interval among theat least three timestamps of the leaf is greater than an age threshold;writing the new data to a first tier storage device when the timeinterval among the at least three timestamps of the leaf is less thanthe age threshold; and writing the new data to a second tier storagedevice when the time interval between a first and a second timestamp ofthe at least three timestamps of the leaf and a second time intervalbetween the second timestamp and a third timestamp of the at least threetimestamps of the leaf are greater than the age threshold.
 12. Thecomputing system of claim 11 wherein the age threshold is based upon, atleast in part, a current garbage collection queue.
 13. The computingsystem of claim 12 wherein the operations further comprise adjusting theage threshold based upon, at least in part, the current garbagecollection queue.
 14. The computing system of claim 13 wherein the agethreshold is adjusted down when fewer physical large blocks (PLBs) areidentified with the age threshold as a candidate for garbage collectionthan are capable of being added to the current garbage collection queue,and wherein the age threshold is adjusted up when more PLBs areidentified with the age threshold as the candidate for garbagecollection than are capable of being added to the current garbagecollection queue.